Total Synthesis of Cardenolides Acospectoside A and Acovenoside B

Acospectoside A (<b>1</b>) and acovenoside B (<b>2</b>), two cytotoxic cardenolides extracted from the venomous South African bush <i>Acokanthera oppositifolia</i>, are distinguished by their unique structural motifs of the l-acovenose moiety at C-3 and a 1β-<i>O</i>-acetylated cardenolide aglycone. Here, we report the synthesis of these cardiac glycosides featuring delicate introductions of the 1-<i>O</i>-acetyl group under acid-catalyzed conditions, 14β-OH by Mukaiyama hydration, and a C17-butenolide moiety by Stille coupling.